This is my first tutorial for mygimptutorial.com
In this tutorial, i will explain to create an original banner.
It seems that the name given for this is isometric banner
That is really simple to realize and i hope you will enjoy it.

Final Image preview

This is what you’ll be able to create

Step 1

Create a new image :

Width : 1200 px

Height : 500 px

Background color : what you want (here i’m choosing white)

Create de new layer and name it : Body

Step 2

Add a square with Square tool and place it in the middle of your layer (body)
Here is the option used :

Add the color you want. Here i’m using 53c1d5

Step 3

Create a new layer and name it Banner

Add a square with the square tools ans select rounded corner with indicator at 100

Color it with the color you want (i’m using 1e4cde)

Step 4

Create a new layer and name it Shadow

Optionnal :
Add 2 guide line at 10px before left side body and 10px after right side body (that will help us to place the shadow)

Select layer shadow and use square tools with the option below :

Create a rounded square just before the top or the bottom of the layer banner.
That is most easily if your are using guideline.

Color your shadow with a darker color than Banner or simply use black color.
Here i’m using : 0c1d53.

Step 5

Keep your selection active, select the layer Banner and press Delete touch on your keyboard
Make a right click on the layer Body and select Alpha to selection
Select the layer Shadow and press Delete touch from your keyboard
Now you can remove guide line if you are using it.

Step 6

Create a new layer and name it Effect
Right click on the layer Banner and select Alpha to selection
Select now the layer Effect and choose Gradient Tools
Choose white color as foreground color
In the option Gradient Tools choose Foreground to transparent

Use the gradient tools like this

With training, you will ba able to do this very quickly
You can try it with circle tools too.
For a square with no rounded corner, you should use the Perspective tools to change the degree of the shadow.